Liquid doping systems and methods for controlled doping of a melt

ABSTRACT

A method of growing a doped monocrystalline ingot using a crystal growing system is provided. The crystal growing system includes a growth chamber, a dopant feeding device, and a feed tube. The method includes preparing a melt of semiconductor or solar-grade material in a crucible disposed within the growth chamber, introducing a solid dopant into the feed tube with the dopant feeding device, melting the solid dopant within the feed tube to a form a liquid dopant, introducing the liquid dopant into the melt below a surface of the melt, and growing a monocrystalline ingot from the melt by contacting the melt with a seed crystal and pulling the seed crystal away from the melt.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claim priority to U.S. Provisional Patent ApplicationSer. No. 62/130,692, filed Mar. 10, 2015, the disclosure of which ishereby incorporated by reference in its entirety.

FIELD

The field relates generally to preparation of single crystals ofsemiconductor or solar-grade material and, more specifically, to aliquid doping system for controlled doping of a melt of semiconductor orsolar-grade material.

BACKGROUND

Single crystal material, which is the starting material for fabricatingmany electronic components such as semiconductor devices and solarcells, is commonly prepared using the Czochralski (“CZ”) method.Briefly, the Czochralski method involves melting polycrystalline sourcematerial, such as polycrystalline silicon (“poly silicon”), in acrucible to form a silicon melt and then pulling a single-crystal ingotfrom the melt.

During the process, dopants are added to the molten source material tomodify the base resistivity of the resulting monocrystalline structure.Dopants are often added to the molten source material in solid form, atleast for p-type and n-type silicon. However, the use of solid dopantspresents several drawbacks.

One drawback is a thermal shock resulting from the temperaturedifference between solid dopants and the molten source material. Thisthermal shock causes the molten source material to solidify underneaththe solid dopant granules, creating “floating boats”. Additionally,quartz particles can form during the formation of the floating boats.These quartz particles may remain in the molten source material longafter the floating boats have melted, resulting in crystal defects orloss of crystal structure.

A further drawback resulting from the addition of solid dopants to themolten source material is contamination of the monocrystalline growingassembly. The impact of solid dopants on the surface of the moltensource material causes the molten source material to splash out of thecrucible and onto various components of the monocrystalline growingassembly, which may result in crystal defects or damage to components inthe assembly.

Yet another drawback to using solid dopants is that many have relativelyhigh evaporation rates, such as indium or antimony. Placing thesedopants directly into the crucible with the semiconductor or othersolar-grade material prior to melting causes the dopant to evaporateduring the heating of the semiconductor or solar-grade material.Additional dopant must be added to compensate for the lost dopant, oftenin significant quantities, resulting in an inefficient use of thedopant. Additionally, the evaporated dopant condenses on variouscomponents of the growing assembly, resulting in contamination of theassembly. Moreover, when low temperature or volatile dopants are addedto a melt, they often remain on the surface of the melt even after thedopants are melted. As a result, there is often a continuous liquid-gasinterface through which the dopant can readily evaporate.

Accordingly, a need exists for more satisfactory systems and methods forintroducing dopants into a melt of semiconductor or solar-gradematerial.

This Background section is intended to introduce the reader to variousaspects of art that may be related to various aspects of the presentdisclosure, which are described and/or claimed below. This discussion isbelieved to be helpful in providing the reader with backgroundinformation to facilitate a better understanding of the various aspectsof the present disclosure. Accordingly, it should be understood thatthese statements are to be read in this light, and not as admissions ofprior art.

BRIEF SUMMARY

In one aspect, a method of growing a doped monocrystalline ingot using acrystal growing system is provided. The crystal growing system includesa growth chamber, a dopant feeding device, and a feed tube. The methodincludes preparing a melt of semiconductor or solar-grade material in acrucible disposed within the growth chamber, introducing a solid dopantinto the feed tube with the dopant feeding device, melting the soliddopant within the feed tube to a form a liquid dopant, introducing theliquid dopant into the melt below a surface of the melt, and growing amonocrystalline ingot from the melt by contacting the melt with a seedcrystal and pulling the seed crystal away from the melt.

In another aspect, a method of introducing a dopant into a melt ofsemiconductor or solar-grade material using a feed tube and a dopantfeeding device is provided. The method includes introducing a soliddopant into the feed tube with the dopant feeding device, melting thesolid dopant within the feed tube to a form a liquid dopant, andintroducing the liquid dopant into the melt below a surface of the melt.

In yet another aspect, a system for growing a single crystal ingot froma melt of semiconductor or solar-grade material is provided. The systemincludes a housing defining a crystal growth chamber, a crucibledisposed within the growth chamber for holding a melt of semiconductoror solar-grade material, a dopant feeding device configured to dispensesolid dopant, and a feed tube. The feed tube is configured to receivesolid dopant from the dopant feeding device and dispense liquid dopantinto the melt. The feed tube defines a dopant outlet, and includes arestrictor nozzle configured to inhibit solid dopant from passingthrough the dopant outlet and to allow liquid dopant to pass through thedopant outlet.

Various refinements exist of the features noted in relation to theabove-mentioned aspects. Further features may also be incorporated inthe above-mentioned aspects as well. These refinements and additionalfeatures may exist individually or in any combination. For instance,various features discussed below in relation to any of the illustratedembodiments may be incorporated into any of the above-described aspects,alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of a crystal growing system including anexample doping system for introducing liquid dopant into a melt;

FIG. 2 is a cross-section of a dopant feeding device suitable for usewith the doping system of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a feed tube of the dopingsystem of FIG. 1; and

FIG. 4 is a flow chart of an example method of growing a dopedmonocrystalline ingot using the crystal growing system of FIG. 1.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION

Referring to FIG. 1, a crystal growing system is shown schematically andis indicated generally at 100 in FIG. 1. The crystal growing system 100is used to produce monocrystalline (i.e., single crystal) ingots ofsemiconductor or solar-grade material (e.g., silicon) by the Czochralski(CZ) method. Although the crystal growing system 100 is described hereinwith reference to a batch or recharge CZ method, the crystal growingsystem 100 may also be used to grow monocrystalline ingots by acontinuous CZ method.

The illustrated crystal growing system 100 generally includes a housing102 defining a growth chamber 104 and an ingot removal chamber 106connected to and positioned above the growth chamber 104. A crucible 108containing a melt 110 of semiconductor or solar-grade material (e.g.,silicon) is positioned within the growth chamber 104, and one or moreheating elements 112 are positioned proximate the crucible 108 forsupplying thermal energy to the system 100. The crystal growing system100 also includes an automatic doping system 114 connected to thehousing 102 for introducing dopant into the melt 110.

The housing 102 includes a lower portion 116, an upper dome 118connected to the lower portion 116, and an elongate tubular portion 120extending generally upward from the upper dome 118. In the illustratedembodiment, the growth chamber 104 is defined by the lower portion 116and the upper dome 118, and the ingot removal chamber 106 is generallydefined by the elongate tubular portion 120. The upper dome 118 includesa central annular opening 122 providing communication between the growthchamber 104 and the removal chamber 106, and a feed port 124 (broadly,an opening) through which dopants may be introduced into the melt 110.In the illustrated embodiment, the feed port 124 is defined along theupper dome 118, although the feed port 124 may be located along anysuitable portion of the housing 102 that enables the doping system 114to function as described herein.

The housing 102 may be made of stainless steel or other suitablematerials. In some embodiments, one or more of the lower portion 116,the upper dome 118, and the tubular portion 120 may include water-cooledstainless steel walls.

The crucible 108 is positioned within the growth chamber 104 and beneaththe removal chamber 106 such that an ingot grown from the melt 110 canbe pulled by a crystal pulling mechanism 126 through the central opening122 in the upper dome 118 and into the removal chamber 106. The crucible108 may be supported within the growth chamber 104 by a susceptor (notshown) and a rotatable shaft (not shown) configured to rotate thecrucible 108 during growth of a crystal ingot.

The crucible 108 may be made of, for example, quartz or any othersuitable material that enables the crystal growing system 100 tofunction as described herein. Further, the crucible 108 may have anysuitable size that enables the crystal growing system 100 to function asdescribed herein. In some embodiments, the crucible 108 has a diameterof between about 16 inches and about 32 inches, more suitably betweenabout 20 inches and about 28 inches, and even more suitably betweenabout 20 inches and about 24 inches. In other embodiments, the crucible108 may have a diameter less than about 16 inches or greater than about32 inches.

The doping system 114 generally includes a dopant feeding device 128 anda feed tube 130. The dopant feeding device 128 is secured to the housing102, and is positioned outside of the growth chamber 104. The feed tube130 is positioned proximate an outlet of the dopant feeding device 128,and extends through the feed port 124 of the housing 102 and into thegrowth chamber 104. The dopant feeding device 128 is configured todispense solid dopant into the feed tube 130, and the feed tube 130 isconfigured to retain solid dopant therein until the dopant is melted,and to introduce liquid dopant into the melt 110.

FIG. 2 is a cross section of an example dopant feeding device 200suitable for use with the doping system 114 of FIG. 1. The exampledopant feeding device 200 is configured to dispense metered quantitiesof solid dopant through an outlet 202 defined at the lowermost point ofthe dopant feeding device 200. The dopant feeding device 200 generallyincludes a fill assembly 204, a hopper 206, and a double valve system208.

The fill assembly 204 includes a fill port 210 and a feed tube 212connected to the fill port 210 and extending from the fill port 210 intothe hopper 206. To load dopant into the dopant feeding device 200,dopant is fed into the fill port 210 and is funneled down into the feedtube 212 and into the hopper 206.

The hopper 206 includes a dopant container 214 for storing dopant, and adopant funnel 216 connected to a lower opening 218 of the dopantcontainer 214. Dopant fed into the fill port 210 is directed into thedopant container 214 by the feed tube 212. Dopant is stored in thedopant container 214, and is released in metered quantities into thedopant funnel 216 using the double valve system 208.

The double valve system 208 includes a lower valve 220 and an uppervalve 222. The lower valve 220 and the upper valve 222 are both operablyconnected to a pneumatic actuator 224. A fill chamber 226 is definedbetween the upper valve 222 and the dopant container 214. The volume ofthe chamber 226 defines the dopant charge or the amount of dopantreleased by the dopant feeding device 200 in a single discharge. Thepneumatic actuator 224 is configured to vertically reciprocate the lowervalve 220 and the upper valve 222 to release metered quantities ofdopant from the chamber 226 into the dopant funnel 216 through the loweropening 218 of the dopant container 214. Dopant released into the dopantfunnel 216 is dispensed from the dopant feeding device 200 into the feedtube 212 through the outlet 202 defined at the lowermost point of dopantfeeding device 200.

The dopant feeding device 200 is described in greater detail inInternational Patent Application No. PCT/IT2013/000161, which is herebyincorporated by reference in its entirety.

Referring again to FIG. 1, the feed tube 130 includes a first end 132, asecond end 134 distal from the first end 132, and an annular sidewall136 extending along a longitudinal axis of the feed tube 130 from thefirst end 132 to second end 134. The feed tube 130 has a dopant inlet138 defined at the first end 132, a dopant outlet 140 (also shown inFIG. 3) defined at the second end 134, and a dopant passage 142 definedtherein extending from the dopant inlet 138 to the dopant outlet 140.Solid dopant dispensed from the dopant feeding device 128 is received inthe feed tube 130 at the dopant inlet 138, and falls through the dopantpassage 142 towards the dopant outlet 140 where the solid dopant isretained until it is melted and released into the melt 110.

In the example embodiment, the feed tube 130 is a telescopic feed tube,including a fixed, inner feed tube 144 and moveable, outer feed tube146. The inner feed tube 144 is secured in a fixed relationship to oneor both of the housing 102 and the dopant feeding device 128, and theouter feed tube 146 is configured to move relative to the inner feedtube 144. The inner feed tube 144 and the outer feed tube 146 areconcentrically arranged about a common longitudinal axis, and the outerfeed tube 146 is configured to move along the longitudinal axis betweenan extended position (shown in FIG. 1) and a retracted position (notshown in FIG. 1). The inner feed tube 144 defines the first end 132 andthe dopant inlet 138 of the feed tube 130, and the outer feed tube 146defines the second end 134 and the dopant outlet 140 of the feed tube130.

The components of the feed tube 130 (e.g., the inner feed tube 144 andthe outer feed tube 146) are suitably made of refractory materials thatremain substantially chemically inert at elevated temperatures. Suitablematerials from which the components of the feed tube 130 may be made ofinclude, for example and without limitation, quartz.

In the example embodiment, the outer feed tube 146 is operativelyconnected to a linear slide mechanism 148 configured to move the outerfeed tube 146 between the extended position (shown in FIG. 1) and theretracted position (not shown in FIG. 1). In some embodiments, thelinear slide mechanism 148 is configured to retract the outer feed tube146 entirely out of the growth chamber 104 when the outer feed tube 146is in the retracted position. In other embodiments, at least a portionof the outer feed tube 146 is positioned within the growth chamber 104when the outer feed tube 146 is in the retracted position. The linearslide mechanism 148 may include any suitable device or combination ofdevices that enable the doping system 114 to function as describedherein including, for example and without limitation, tracks, rails,rollers, bearing mechanisms, actuators, and combinations thereof.

In the example embodiment, the linear slide mechanism 148 includes arail 150, coupling members 152 slidably connected to the rail 150 andattached to the outer feed tube 146, and an actuator (not shown)operably connected to one or both of the outer feed tube 146 and thecoupling members 152. The actuator of the linear slide mechanism 148 isconfigured to move the coupling members 152 along the rail 150, and movethe outer feed tube 146 between the extended and retracted positions. Inother suitable embodiments, linear actuating devices other than a linearslide mechanism may be used to move the outer feed tube 146 between theextended and retracted positions.

FIG. 3 is an enlarged cross-sectional view of the feed tube 130,specifically, the outer feed tube 146. When the outer feed tube 146 isin the extended position, as shown in FIG. 3, the dopant outlet 140 issubmerged at a depth 302 below a surface 304 of the melt 110. The outerfeed tube 146 includes a restrictor nozzle 306 at the second end 134 ofthe feed tube 130 configured to inhibit solid dopant 308 from passingthrough the dopant outlet 140 and to allow liquid dopant to pass throughthe dopant outlet 140.

The restrictor nozzle 306 includes a conical portion 310 extendingradially inward from the annular sidewall 136 to the dopant outlet 140at an angle 312, and defines a diameter 314 of the dopant outlet 140sized to inhibit solid dopant 308 from passing therethrough. The dopantoutlet 140 may have any suitable diameter 314 that enables the dopingsystem 114 to function as described herein, and may vary depending onthe type of solid dopant 308 used to dope the melt 110. In someembodiments, for example, the dopant outlet 140 has a diameter ofbetween about 1 millimeter (mm) and about 4 mm, and is configured toreceive solid dopant 308 having an average particle size of betweenabout 2 mm and about 5 mm.

In some embodiments, the angle 312 at which the conical portion 310 ofthe restrictor nozzle 306 extends inward from the sidewall 136 isbetween about 15° and about 35° and, more suitably, between about 20°and about 30°. In the illustrated embodiment, the conical portion 310extends inward from the sidewall 136 at an angle of about 25°. Moreover,in the illustrated embodiment, the conical portion 310 of the restrictornozzle 306 extends inward from the sidewall 136 at an angle 312 suchthat, when the feed tube 130 is in the extended position, the conicalportion 310 and the reminder of the restrictor nozzle 306 are generallyoriented at the same angle with respect to the surface of the melt 110,as shown in FIG. 3.

Solid dopant 308 introduced into the feed tube 130 is retained withinthe dopant passage 142 by the restrictor nozzle 306 at the second end134 of the feed tube 130 until the solid dopant 308 is melted by heatfrom the melt 110 and/or the heating elements 112. As the solid dopantmelts and forms liquid dopant, the liquid dopant flows out of the feedtube 130 through the dopant outlet 140 and into the melt 110. The shapeand orientation of restrictor nozzle 306 and, in particular, the angle312 at which conical portion 310 extends from the sidewall 136facilitate dispensing all liquid dopant from within the feed tube 130.

In the example embodiment, the restrictor nozzle 306 is also configuredto inhibit liquid melt material from flowing upward into the feed tube130 through the dopant outlet 140, which can damage or impairoperability of the feed tube 130 (e.g., by clogging the dopant outlet140). In particular, the restrictor nozzle 306 is sized and shaped, andmade of suitable materials so that the interfacial surface energybetween the melt 110 and the restrictor nozzle 306 and the surfacetension of the melt 110 inhibits melt material from flowing upward intothe feed tube 130 through the dopant outlet 140. In the exampleembodiment, the outer feed tube 146 is suitably made of quartz, and hasa dopant outlet 140 with a diameter in the range of between about 1 mmand about 4 mm. The outer feed tube 146 is suitable for introducingliquid dopant into the melt 110 at a depth 302 up to about 5 mm. Inother embodiments, the outer feed tube 146 may be made of materialsother than quartz, such as other refractory materials that remain inertat elevated temperatures, and have a dopant outlet with a diameter lessthan about 1 mm or greater than about 4 mm.

In use, the crystal growing system 100 is used to grow dopedmonocrystalline ingots, such as antimony-doped single crystal siliconingots, from the melt 110. More specifically, the melt 110 is preparedin the crucible 108 by charging the crucible 108 with feedstockmaterial, such as chunk polycrystalline silicon. The feedstock materialis melted in the crucible 108 using heating elements 112 to form themelt 110 of semiconductor or solar grade material. Dopants are added themelt 110 using the automatic doping system 114 by dispensing soliddopant from the dopant feeding device 128 into the feed tube 130,melting the solid dopant within the feed tube 130 to form liquid dopant,and introducing the liquid dopant into the melt 110 through the dopantoutlet 140 at a depth below the surface of the melt 110. When a desiredamount of dopant has been added to the melt 110, a monocrystalline ingotis grown from the melt 110 by contacting the melt 110 with a seedcrystal (not shown) to initiate crystal growth, and subsequently pullingthe seed crystal away from the melt to grow the monocrystalline ingot.

FIG. 4 is a flow chart of an example method 400 of growing a dopedmonocrystalline ingot using the crystal growing system 100 describedabove with reference to FIGS. 1-3. The method 400 generally includespreparing 410 a melt of semiconductor or solar-grade material in thecrucible 108 disposed within the growth chamber 104, introducing 420 asolid dopant into the feed tube 130 with the dopant feeding device 128,melting 430 the solid dopant within the feed tube 130 to a form a liquiddopant, introducing 440 the liquid dopant into the melt 110 below thesurface 304 of the melt 110, and growing 450 a doped monocrystallineingot from the melt by contacting the melt with a seed crystal andpulling the seed crystal away from the melt.

The melt 110 may be prepared, for example, by charging the crucible 108with solid feedstock material and melting the feedstock material withheating elements 112. The semiconductor or solar-grade material used toprepare the melt 110 may include, for example and without limitation,silicon.

The doping system 114 and the method 400 are particularly suitable foruse with dopants having a relatively low melting temperature relative tothe melting temperature of the semiconductor or solar-grade materialused to prepare the melt 110. In some embodiments, for example, thedopant used to dope the melt 110 has a melting temperature less than themelting temperature of the semiconductor or solar-grade material used toprepare the melt. In some particular embodiments, such as when siliconis used to prepare the melt, the dopant used to dope the melt isselected from the group consisting of aluminum, gallium, indium,thallium, and antimony, although any suitable n-type or p-type dopantmay be used with the doping system 114 and the method 400.

In some embodiments, the method 400 further includes positioning thedopant outlet 140 of the feed tube 130 at a depth 302 below the surface304 of the melt 110. In some embodiments, for example, all or part ofthe feed tube used to carry out the method 400 is moveable between anextended position, in which the feed tube is positioned within thegrowth chamber 104 and the dopant outlet is positioned below the surfaceof the melt 110, and a retracted position, in which the feed tube isremoved from the growth chamber 104. The dopant outlet may be positionedat any suitable depth below the surface of the melt that enables thedoping system 114 to function as described herein. In some embodiments,for example, the dopant outlet is positioned at a depth of at leastabout 1 cm below the surface of the melt and, more suitably, at a depthof between about 1 cm and about 5 cm below the surface of the melt.

In some embodiments, solid dopant is introduced into the feed tube whilethe feed tube is in the extended position and is positioned within thegrowth chamber. In other embodiments, solid dopant is introduced intothe feed tube while the feed tube is in the retracted position andremoved from the growth chamber, and the feed tube is subsequently movedto the extended position such that solid dopant within the feed tube canbe melted by heat from the melt.

In some embodiments, introducing 420 a solid dopant into the feed tubeincludes introducing multiple charges of solid dopant into the feed tubewithout removing the feed tube from growth chamber. For example,introducing 420 a solid dopant into the feed tube may includeintroducing a first charge of solid dopant into the feed tube and, afterthe first charge of solid dopant is melted and introduced into the melt,introducing a second charge of solid dopant into the feed tube withoutremoving the feed tube from the growth chamber.

In some embodiments, introducing 440 the liquid dopant into the meltincludes introducing the liquid dopant into the melt while themonocrystalline ingot is being grown. In some embodiments, for example,the feed tube 130 is held in the extended position after crystal growthis initiated, and liquid dopant is intermittently or continuouslyintroduced into the melt 110 while the monocrystalline ingot is grown.Thus, the method 400 can be used to dope a melt in a batch CZ process orin a continuous CZ process.

Embodiments of the doping systems and methods described herein provideseveral advantages over known doping systems and methods. For example,the doping systems and methods described herein introduce dopants inliquid form below a surface of a melt of semiconductor or solar-gradematerial. By introducing dopants in liquid form, the doping systems andmethods of the present application facilitate inhibiting thermal shockand freezing of melt material, which can result in loss of crystalstructure of a growing monocrystalline ingot. Moreover, by introducingdopants as a liquid below the surface of a melt, the doping systems andmethods of the present application facilitate reducing evaporation ofelemental dopant and dopant compounds (e.g., dopant oxide species) thatmight otherwise deposit on view ports on a crystal growing system andinhibit an operator's ability to monitor a crystal growing operation. Inaddition, introducing dopants as a liquid below the surface of a meltinhibits splashing of the melt, which might otherwise cause crystaldefects or damage to components of the crystal growing system.

The doping systems and methods of the present application thusfacilitate doping semiconductor or solar-grade melts with lowtemperature dopants, such as aluminum, gallium, indium, thallium, andantimony, while alleviating many of the problems associated with usinglow temperature dopants to dope semiconductor or solar-grade melts.

When introducing elements of the present invention or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

1. A method of growing a doped monocrystalline ingot using a crystalgrowing system including a growth chamber, a dopant feeding device, anda feed tube, the method comprising: preparing a melt of semiconductor orsolar-grade material in a crucible disposed within the growth chamber;introducing a solid dopant into the feed tube with the dopant feedingdevice; melting the solid dopant within the feed tube to a form a liquiddopant; introducing the liquid dopant into the melt below a surface ofthe melt; and growing a monocrystalline ingot from the melt bycontacting the melt with a seed crystal and pulling the seed crystalaway from the melt.
 2. The method of claim 1, wherein the feed tubeincludes a first end defining an inlet for receiving solid dopant fromthe dopant feeding device and a second end having a dopant outletdefined therein, the method further comprising positioning the dopantoutlet below the surface of the melt.
 3. The method of claim 2, whereinpositioning the dopant outlet below the surface of the melt includespositioning the dopant outlet at a depth of at least about 1 cm belowthe surface of the melt.
 4. The method of claim 2, wherein positioningthe dopant outlet below the surface of the melt includes positioning thedopant outlet at a depth of between about 1 cm and about 5 cm below thesurface of the melt.
 5. The method of claim 1, wherein introducing asolid dopant into the feed tube includes introducing the solid dopantinto the feed tube while the feed tube is positioned within the growthchamber.
 6. The method of claim 1, wherein introducing a solid dopantinto the feed tube includes introducing a first charge of solid dopantinto the feed tube and, after the first charge of solid dopant ismelted, introducing a second charge of solid dopant into the feed tubewithout removing the feed tube from the growth chamber.
 7. The method ofclaim 1, wherein introducing a solid dopant into the feed tube includesintroducing the solid dopant into the feed tube while the feed tube isremoved from the growth chamber.
 8. The method of claim 1, whereinintroducing the liquid dopant into the melt includes introducing theliquid dopant into the melt while the monocrystalline ingot is beinggrown.
 9. The method of claim 1, wherein introducing the liquid dopantinto the melt includes introducing the liquid dopant into the melt at adepth of between about 1 cm and about 5 cm below a surface of the melt.10. The method of claim 1, wherein the solid dopant is selected from thegroup consisting of aluminum, gallium, indium, thallium, and antimony.11. The method of claim 1, wherein the melt is a silicon melt. 12-18.(canceled)
 19. A system for growing a single crystal ingot from a meltof semiconductor or solar-grade material, the system comprising: ahousing defining a crystal growth chamber; a crucible disposed withinthe growth chamber for holding a melt of semiconductor or solar-gradematerial; a dopant feeding device configured to dispense solid dopant;and a feed tube configured to receive solid dopant from the dopantfeeding device and dispense liquid dopant into the melt, the feed tubedefining a dopant outlet and including a restrictor nozzle configured toinhibit solid dopant from passing through the dopant outlet and to allowliquid dopant to pass through the dopant outlet.
 20. The system of claim19, wherein at least a portion of the feed tube is moveable from aretracted position to an extended position in which the dopant outlet ispositioned below a surface of the melt.
 21. The system of claim 19,wherein the housing has a feed port defined therein for introducingdopant into the growth chamber, the feed tube extending through the feedport.
 22. The system of claim 19, wherein the feed tube includes asidewall defining a dopant passage, the restrictor nozzle including aconical portion extending radially inward from the sidewall to thedopant outlet.
 23. The system of claim 22, wherein the conical portionextends radially inward from the sidewall at an angle of between about20° and about 30°.
 24. The system of claim 19, wherein the dopant outlethas a diameter of between about 1 millimeter and about 4 millimeters.25. The system of claim 19, wherein the feed tube includes an outer feedtube and an inner feed tube at least partially disposed within the outerfeed tube, the outer feed tube including the restrictor nozzle.
 26. Thesystem of claim 25, wherein the outer feed tube is configured to moverelative to the inner feed tube between a retracted position and anextended position is which the dopant outlet is positioned below thesurface of the melt.
 27. The system of claim 19, wherein the feed tubeis made of quartz.